During milling of various materials with coated cemented carbide cutting tools, the cutting edges are regarded as being worn according to different wear mechanisms. Wear types, such as chemical wear, abrasive wear and adhesive wear, are rarely encountered in a pure state, and complex wear patterns are often the result. The domination of any of the wear mechanisms is determined by the application, and is dependent on properties of the machined material, applied cutting parameters, and the properties of the tool material. The machinability of cast irons can vary considerably between the various groups but also within a certain group. Small variation in the chemical composition or the micro-structure, related to the casting technique, can have significant influence on the tool life.
In general, the different cast irons are very demanding when it comes to wear resistance and therefore chemical vapor deposition (CVD)-coated inserts have been commonly used. However, in some applications these inserts do not have the combination of edge toughness and wear resistance needed.
EP 1205569 discloses a coated milling insert particularly useful for milling of grey cast iron with or without cast skin under wet conditions at low and moderate cutting speeds and milling of nodular cast iron and compacted graphite iron with or without cast skin under wet conditions at moderate cutting speeds. The insert is characterised by a WC—Co cemented carbide with a low content of cubic carbides and a highly W-alloyed binder phase and a coating including an inner layer of TiCxNy with columnar grains followed by a layer of κ-Al2O3 and a top layer of TiN.
EP 1655391 discloses coated milling inserts particularly useful for milling of grey cast iron with or without cast skin under dry conditions at preferably rather high cutting speeds and milling of nodular cast iron and compacted graphite iron with or without cast skin under dry conditions at rather high cutting speeds. The inserts are characterised by a WC—Co cemented carbide with a low content of cubic carbides and a highly W-alloyed binder phase and a coating including an inner layer of TiCxNy with columnar grains followed by a wet blasted layer of α-Al2O3.
What is needed is a coated cutting tool with enhanced performance for wet or dry milling of cast irons. The invention is directed to these, as well as other, important needs.